Short answer will be the P6 (from w Germany)is mostly a early LE service pistol. And P225 is for civilian. P6 has a different spring set in it to make the trigger pull/hammer and slide harder. The barrel design for ball ammo only. The easy way to tell P6 from P225 is the cut slug on the hammer. It's a proof that pistol has under go a drop test. P225 is a civilian version of P6. Lighter spring set, polished/re-ramped to take the hollow point. Usually in a better shape the most trade-in P6 you would see. There is also a P225 used by Swiss LEO/Millitary. It has the euro style mag release. I don't know what kind of spring set they use in it or if they can use HP ammo. Many reseller try to pass this trade-in as the civilian P225 and ask for the same price. I would pick up a P6 for a easy shooter, if I can find one. Spring set is cheap and easy to find.
The P 225 is the civilian version of the the German police service pistol P6. It was developped around the requirements for a police pistol back in its day. The P220 was too large. The P1 is the old civilian Walther P 38, # P1 - P38, Walther # P2 - Sig 210 # P3 - 600/43, Astra # P4 - shorter improved version of P1 # P5 - P5, Walther # P6 - P225, Sig Sauer # P7 - PSP, HK # P8 - USP Variante, HK # P9 - P99, Walther # P10 - USP Compact, HK # P11 - P11, HK # P12 - USP Tactical .45, HK
The most noticeableable, external difference (for immediate ID): P225 has a tang hammer P6 has a round hammer, The P6's round hammers usually have a cut through one part (I'm not 100% sure they all have this, but I've never seen one that didn't).
Over on Sigforum they had a member who was German po-po and he explained the cut in the hammer as a way to se if someone dropped the gun on its hammer damaging the sear/trigger. Apparently a copper over there dropped it on its hamer and the gun later went bang when it wasn't supposed to. The theory was it the hammer was damaged on the outside it could be damaged on the inside.
About the same difference between a Beretta M9 and a 92FS. One is the Mil/LEO designation one is the civilian. Basically the same gun.
Later P6s have the same feed ramp as the commercial P225. If you have an older P6 the ramp can be rectified to feed HPs for about $25. Details at Sigforum.com
